National Coral Reef Monitoring Program
Climate Monitoring Brief: St. Croix, USVI
New Subsurface Temperature Recorder deployed at White Shoal in Dry Tortugas National Park
Atlantic Oceanographic & Meteorological Laboratory Coral Program
University of Miami Cooperative Institute of Marine and Atmospheric Science
National Oceanic Atmospheric Administration
N. Besemer, A. Palacio, A. Webb, G. Kolodziej, M. Chakraborty, I. Enochs - October 2022
About this summary brief
The NOAA Atlantic Oceanographic and Meteorological Laboratory (AOML) conducts the long-term National Coral Reef Monitoring Program (NCRMP) to track the status and trends of coral reef ecosystems of the U.S. Atlantic and Caribbean coral reef jurisdictions. This FY21 summary brief provides an overview of the most recent survey efforts.
Expedition summary
- The most recent NCRMP Atlantic climate monitoring took place in St. Croix in the US Virgin islands from September 4th to September 9th 2022
- 16 different sites were visited by four team members and collaborators completing a total of 45 dives.
- These sites represent temporal‐resolution monitoring with moored instruments at fixed time‐series which are placed on depth gradient to assess how vertical structure affects reef status and trends.
Data collection
- Subsurface temperature recorders (STRs) were recovered and redeployed at all 4 transects, each one composed by 3-4 depths (Fig. 1). Overall, more than 4 million temperature observations were collected:
| Transect | 01m | 05m | 15m | 25m | Total |
|---|---|---|---|---|---|
| east | 314,505 | 314,508 | 315,351 | 315,345 | 1,259,709 |
| north | NA | 313,850 | 313,887 | 257,270 | 885,007 |
| south | 231,351 | 315,094 | 315,095 | 315,091 | 1,176,631 |
| west | NA | 314,240 | 314,245 | 314,243 | 942,728 |
- At Salt River, the north side of St. Croix, short term instruments (72h) were deployed to monitor daily fluctuations in:
- Current: 294 observations
- pH: 294 observations
- Light: 290 observations
- Carbonate Chemistry: 15 samples collected
- Additionally, changes in benthic cover and carbonate production were monitored at all 15m sites by recording:
- Bioerosion: 39 Bioerosion Monitoring Units (BMUs) collected, 40 redeployed
- Calcification: 18 Calcification Accretions Units (CAUs) collected, 20 redeployed
- Benthic cover: 6 landscape mosaics (Salt River Only)
- Carbonate budget surveys: Benthic cover, sponge, urchin and parrotfish surveys completed at 6 transects (Salt River Only)
Figure 1: Study sites and depths in Dry Tortugas National Park area
Temperature
Three years of temperature measurements were retrieved and processed from 14 sites (depths). Temperature was measured using SeaBird Electronics Subsurface Temperature Recorders (STR)s that collected data at 5-minute intervals.
Figure 2: Temperature conditions at four transects in Saint Croix (east, west, north and south) representing a depth gradient (1m, 5m, 15mand 25m). CHANGE THIS: Data were collected from September 2019 to September 2022. DID ANY NOT LOG THE FULL TIME?)
Temperature values were similar among the transects and depths depths with the lowest temperatures generally occurring in March (mean: 26.56 \(^\circ\)C, min: 25.64 \(^\circ\)C, max: 28.27 \(^\circ\)C) and the the highest temperatures in September(mean: 29.68 \(^\circ\)C, min: 27.22 \(^\circ\)C, max: 32.11\(^\circ\)C). The south 1m station presented the highest temperature variability and the maximum temperature values recorded in October 2021 (32.16\(^\circ\)C) and September 2020 (32.11\(^\circ\)C) (Fig. 2).
Diurnal Suite Deployment
At the North 15m site, Salt River Bay, additional instruments were deployed for a 72-hour diurnal suite that monitored pH, temperature, light and current speed (Fig. 3). The SeaFET pH logger, EcoPAR and Tiltmeter collected measurements at 15-minute intervals.
Figure 3: Salt River Bay (N 15m) diurnal suite monitoring from Sept 5th to Sept 8th. Top panel: pH and temperature from SeaFET. Bottom panel: Photosynthetically Available Radiation (PAR) and current speed from EcoPAR and Tiltmeter. Grey blocks denote night time throughout sequence of the plot. Instruments measured parameters every 5 minutes.
As part of the diurnal suite, discrete water samples were collected at three-hour intervals (n=15) using Subsurface Automatic Samplers (SAS). These samples will be analyzed for Total Alkalinity (TA), Dissolved Inorganic Carbon (DIC), and Spectrophotometric pH (SpecpH). Using these metrics we can get the calculated values for pCO2 and aragonite saturation state. For more information on SAS vist https://www.coral.noaa.gov/accrete/sas/
Submered Automated Samplers (SAS) deployed to collect water samples every 3 hours
Carbonate budgets
At Salt River Bay, 6 transects were established in 2019 and surveyed to obtain carbonate budgets which quantify reef building organisms and reef eroders to determine if a reef is net growing or net eroding. (Fig. 4).We revisited this site to complete individual surveys on benthic cover, parrotfish, urchin and bioeroding sponge abundance to see if there is a change in the reef budget over 3 years.
Figure 4: EXPLAIN THIS PLOT.
Other Deliverables
- Calcification Accretion Units (CAUs) and Bioerosion Monitoring Units (BMUs) were collected and redeployed for the next sampling cycle. CAUs are processed by the Pacific Climate group and the data will be available within a year. BMUs will be dried and cleaned using a hydrogen peroxide solution. These samples will be weighed and scanned using a Macro CT scanner and then compared to their pre-scans to quantify bioerosion. Data will be available in a year. Please reference previous datasets for more information.
CAU and BMU pair before retreval after being deployed for 3 years. CAUs are 2 parallel PVC plates to quantify settled accretors. BMU is mounted coral skeleton installed at the base of the metal stake and has been encrusted.
- Landscape mosaics (n=6) and carbonate budget surveys (n=6) were completed to monitor changes in benthic cover and carbonate production
